Cyclobutanetetracarboxylate compound and preparation method thereof

ABSTRACT

The invention provides a cyclobutanetetracarboxylate compound of general formula (I) and a preparation method thereof:  
                 
 
in which R and R 1  are as defined in the specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cyclobutanetetracarboxylate compoundand a preparation method thereof.

2. Description of the Prior Art

Cyclobutanetetracarboxylic dianhydrides are important monomer materialsfor the preparation of an alignment film useful for flat panel displays.Japanese Laid-open Hei 2003-192685 discloses a process for producingcyclobutanetetracarboxylic dianhydride comprising irradiating maleicanhydride to synthesize the cyclobutanetetracarboxylic dianhydride. Thisprocess, however, suffers from the shortcomings of a low yield in theproduction of the butane structure.

To overcome the above shortcomings, the inventors of the subjectapplication developed a new synthesis route comprising synthesizing acyclobutanetetracarboxylate, hydrolyzing thecyclobutanetetracarboxylate, and dehydrating the hydrolyzed product toobtain the corresponding cyclobutanetetracarboxylic dianhydride. The newroute according to the present invention achieves an improved yield ofthe desired compounds.

SUMMARY OF THE INVENTION

One of the objects of the invention is to provide acyclobutanetetracarboxylate compound.

Another object of the invention is to provide a process for preparingthe cyclobutanetetracarboxylate compound.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a cyclobutanetetracarboxylate compound of thegeneral formula (I):

in which:

-   R can be the same or R is different from each other and    independently represents hydrogen or a halogen or a monovalent    organic radical; and R₁ is a C₁-C₄ alkyl.

There are no special requirements for the species of the monovalentorganic radical suitable for the present invention. Preferably, themonovalent organic radical is a C1-C4 alkyl, which can bestraight-chained, branched, or cyclic; and more preferably, is methyl,ethyl, propyl, isopropyl, butyl, or isobutyl.

The invention further provides a process for preparing thecyclobutanetetracarboxylate compound of formula (I). The inventiveprocess comprises the steps of:

(a) conducting an esterification reaction of a diacid compound ofgeneral formula (II)

(in which R is as defined hereinbefore) with an alcohol of generalformula (III)R₁—OH  Formula (III)in the presence of an acidic solvent to obtain a precursor compound ofgeneral formula (IV)

(b) conducting a cyclization reaction by irradiating the precursorcompound of general formula (IV) with an energy ray to obtain thecyclobutanetetracarboxylate compound of general formula (I).

The acidic solvent used in the inventive process can also be used as acatalyst to enhance the reaction rate. Suitable acidic solvent can be amono-protonic inorganic acid, a multi-protonic inorganic acid, or anorganic acid, which preferably is hydrochloric acid or sulfuric acid.

The esterification reaction in step (a) of the inventive process isobvious to persons skilled in the art. The suitable species of thealcohol will vary with the desired product to be obtained and mayinclude, for example, methanol, ethanol, propanol, or isopropanol. Thediacid compound used in the present invention is a fumaric acid. Theesterification reaction is conducted at a temperature ranging from 60 to110° C. for 2 to 20 hours.

The energy ray used in step (b) of the inventive process refers to alight source with a wavelength of from 200 to 600 nm, preferably anultraviolet light. In general, the irradiation time will vary with thewavelength of the energy ray and is normally in the range of from about30 minutes to 30 hours. In addition, if desired, the reaction of step(b) can be conducted in the presence of a solvent that is beneficial tothe progress of the reaction. Examples of such solvent include ethylacetate, acetone, water, or a mixture thereof.

The compound of formula (I) according to the present invention can becatalytically hydrolyzed in the presence of an acid or a base in aconventional manner known to persons skilled in the art to form thecorresponding cyclobutanetetracarboxylic acid, which can be furtherdehydrated to form the corresponding cyclobutanetetracarboxylicdianhydride.

The present invention will be further described in the followingexample. However, the example will not make any limitations to the scopeof the invention. Any modifications or alterations on the invention thatcan be easily accomplished by persons skilled in the art are encompassedin the disclosure of the specification and the accompanying claims.

EXAMPLE

Synthesis of a cyclobutanetetracarboxylic dianhydride

In a 5-liter flask, methanol (3000 ml, 75 mol) and then fumaric acid(1160 g, 10 mol) and concentrated sulfuric acid (10 ml, 0.2 mol) wereadded. The reaction was conducted at a controlled temperature of 75° C.for 10 hours and then cooled to room temperature. The resultant solidwas collected by vacuum filtration and washed with methanol to obtaindimethyl fumarate (1224 g, 8.5 mol).

The dimethyl fumarate (1224 g, 8.5 mol) and water (4000 ml) were addedto a 6-liter flask and irradiated by 365 nm ultraviolet lights for 7hours. The resultant solid in the flask was vacuum filtered to obtaintetramethyl cyclobutane-1,2,3,4-tetracarboxylate (1224 g, 4.25 mol).

The resultant tetramethyl cyclobutane-1,2,3,4-tetracarboxylate (1224 g,4.25 mol) and aqueous hydrochloric acid (3000 ml) were added to a5-liter flask; reacted at a controlled temperature of 85° C. for 24hours; cooled to room temperature; concentrated; and dried to obtaincyclobutane-1,2,3,4-tetracarboxylic acid (870 g, 3.75 mol).

The cyclobutane-1,2,3,4-tetracarboxylic acid (501 g, 2.16 mol) andacetic anhydride (3000 ml) were added to a 5-liter flask and reacted ata controlled temperature of 150° C. for 24 hours. The reaction wascooled to room temperature; concentrated; and dried to obtain1,2,3,4-cyclobutanetetracarboxylic dianhydride (573 g, 2.93 mol).

1. A cyclobutanetetracarboxylate compound of general formula (I):

in which: R can be the same or R is different from each other andindependently represents hydrogen or a halogen or a monovalent organicradical; and R₁ is a C₁-C₄ alkyl.
 2. The cyclobutanetetracarboxylatecompound of claim 1, wherein said monovalent organic radical is astraight-chained, branched, or cyclic C₁-C₄ alkyl.
 3. Thecyclobutanetetracarboxylate compound of claim 1, wherein said monovalentorganic radical is methyl, ethyl, propyl, isopropyl, butyl, or isobutyl.4. A process for the preparation of the cyclobutanetetracarboxylatecompound as defined in claim 1, comprising: (a) conducting anesterification reaction of a diacid compound of general formula (II)

(in which R is as defined hereinbefore) with an alcohol of generalformula (III)R₁—OH  Formula (III) in the presence of an acidic solvent to obtain aprecursor compound of general formula (IV)

(b) conducting a cyclization reaction by irradiating the precursorcompound of general formula (IV) with an energy ray to obtain thecyclobutanetetracarboxylate compound of general formula (I).
 5. Theprocess of claim 4 wherein the alcohol of general formula (III) ismethanol, ethanol, propanol, or isopropanol.
 6. The process of claim 4wherein the reaction of step (a) is conducted at a temperature from 60to 110° C.
 7. The process of claim 4 wherein the reaction of step (a) isconducted for 2 to 20 hours.
 8. The process of claim 4 wherein theenergy ray used in step (b) is a light source having a wavelength offrom 200 to 600 nm.
 9. The process of claim 4 wherein the energy rayused in step (b) is an ultraviolet light.
 10. The process of claim 4wherein the reaction of step (b) is conducted for 30 minutes to 30hours.
 11. The process of claim 4 wherein the reaction of step (b) isconducted in the presence of a solvent.
 12. The process of claim 11wherein the solvent is ethyl acetate, acetone, water, or methanol, or amixture thereof.